MECHANICS AND USEFUL AKTS. 33 



I have ever felt a lively interest, although it has only been iu my power to 

 bestow on it a casual attention, or cultivate one limited portion of the wide range 

 which it embraces. Indeed Geology, the science to which I now allude, has, 

 during the last twenty years, made such rapid strides, that those who endea- 

 vored from an early period of life to follow at a humble distance the footsteps 

 of the great leaders in that science, have, if I may judge of others by myself, 

 been often distanced in the race, and when they endeavored to make good 

 their lost ground, found themselves transported into a new, and to them an 

 almost unknown region. Thus the thorough exploration which has taken 

 place of the Silurian and Cambrian systems, has added a new province 

 ought I not rather to say, a new kingdom ? to the domain of Geology, and 

 has carried back the records of the creation to a period previously as much 

 unknown to us as were the annals of the Assyrian dynasties before the dis- 

 coveries of Sir Henry Rawlinson. I might also be disposed to claim for the 

 recent investigations of botanists some share in fixing the relative antiquity 

 of particular portions of the globe, for from the Floras they have given us of 

 different islands in the Great Pacific, it would appear that the families of 

 plants which characterize some groups are of a more complicated organization 

 than those of another. Thus, whilst Otaheite chiefly contains Orchids, Apocy- 

 nese, Asclepiadese, and Urticeee ; the Sandwich Islands possess Lobeliacese 

 and Goodenovias; and the Galapagos Islands, Xew Zealand, and Juan 

 Fernandez, Composite, the highest form, perhaps, of dicotyledonous plants. 

 In deducing this consequence, however, I am proceeding upon a principle 

 which has lately met with opposition, although it was formerly regarded as 

 one of the axioms in Geology. Amongst these, indeed, there was none which 

 a few years ago seemed so little likely to be disputed as that the classes of 

 animals and vegetables which possessed the most complicated structure were 

 preceded by others of a more simple one ; and that when we traced back the 

 succession of beings to the lowest and the earliest of the sedimentary forma- 

 tions, we arrived at length at a class of rocks, the deposition of which must be 

 inferred, from the almost entire absence of organic remains, to have followed 

 very soon after the first dawn of creation. But the recognition of the foot- 

 steps and remains of reptiles hi beds of an earlier date than was before as- 

 signed to them, tended to corroborate the inferences which had been previously 

 deduced from the discovery, in a few rare instances, in rocks of the secondary 

 age, of mammalian remains ; and thus has induced certain eminent geologists 

 boldly to dispute, whether, from the earliest to the latest period of the earth's 

 history, any gradation of beings can in reality be detected. Into this con- 

 troversy I shall only enter at present, so far as to point out an easy method 

 of determining the fact, that organic remains never can have existed in a 

 particular rock, even although it may have been subjected to such a meta- 

 morphic action as would have obliterated all traces of their presence. This 

 is simply to ascertain, that the material in question is utterly destitute of phos- 

 phoric acid; for inasmuch as every form of life appears to be essentially 

 associated with this principle, and as no amount of heat would be sufficient 

 to dissipate it when in a state of combination, whatever quantity of phos- 

 phoric acid had in this manner been introduced into the rock, must have 



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